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THE END OF THE BEGINNING

In July, 1972, BOAC and Air France signed contracts for a total of nine Concordes, an event described by Sir George Edwards, chairman of BAC, in the Churchillean phrase as "the end of the beginning." Six months later, Pan American and TWA decided to cancel their options, an event that was hailed in some quarters as the beginning of the end.

BOAC had already announced that it planned to operate Concorde on routes to the USA, the Far East, Australia and South Africa. Air France had not made any public statement of its intentions, but it was expected that a service from Paris to Rio de Janeiro would be one of its first objectives. A ministerial statement in Parliament gave the information that the cost to BOAC of their five Concordes, including spares, was £125 millions. It was a heavy capital commitment, but the high unit cost of the aircraft has to be considered in relation to its unit productivity; each Concorde will be capable of carrying more passengers across the North Atlantic in a year than an ocean liner of the size of the Queen Elizabeth 11.

Both BOAC and Air France firmly denied suggestions that their contracts had been negotiated under any form of government duress. Nevertheless, it was generally accepted that the acid test of Concorde's marketability would come when the leading American carriers were required to decide on their options. In the meantime, there were two other heartening developments for the Concorde builders.

First, during a visit to London, the Shah of Iran reaffirmed that it was Iran Air's intention to order two Concordes, with a third on option. He said: "This is something that is finished and done. The actual date and delivery will be discussed later." (At the time of writing, several years later, the contract negotiations with Iran Air are in the final stages and the outcome probably depends more on political decisions elsewhere in the world than on the technical and commercial qualities of the aircraft.)

The second encouraging development was the addition of the Chinese national civil aviation corporation to the list of potential Concorde customers. After lengthy exchanges between France and China, a preliminary purchase agreement for the supply of two Concordes from the Toulouse assembly line was signed in Paris on July 24. A second agreement, for delivery of a third aircraft from the BAC line, was signed in Peking a month later.

Thus, over the space of two months, contracts and preliminary purchase agreements had been signed, representing a total commitment to Concorde of several hundred millions of pounds. Market prospects suddenly seemed brighter, and once again a slightly unreal euphoria was being generated in some quarters. Before long, however, a chill wind began to blow from the direction of the USA. One of the conditions of the first option agreements had been that, within six months of' contract signature by BOAC or Air France, the option-holders had to reach a final decision on whether or not to convert their options into firm orders. Now BOAC and Air France had signed and, in a phrase then current, "the clock had begun to tick."

The main sales effort of the manufacturers was now concentrated on Pan American and TWA. If these, the two biggest long-haul operators in the world, could be persuaded to endorse Concorde by converting options into orders, many other airlines would follow their example. If they cancelled, it was likely that other airlines would do the same and decide to wait.

For the Concorde team, the stakes could hardly have been higher and the game could hardly have been played at a worse time After a long reign as the most successful airline in the world, Pan American had had a series of disastrously unprofitable years. Some of the troubles had been caused by an over-extension of operations in the "fat" years, but the main problem was the excess capacity resulting from the heavy investment in wide-bodied jets. In January, 1973, TWA were also running at a loss, although not to the same extent.

Negotiations went on almost under the eyes of the world news media, a fact that added to the pressure on both sides. "It was like working in a goldfish bowl," was the way one BAC man put it. As was to be expected, the main discussions centred around the economics of the aircraft. The performance guarantees that the makers were prepared to offer would probably have been found acceptable but there was a difference of opinion on the likely revenue earning capacity of the aircraft.

Both airlines considered that the BAC Aerospatiale estimates of the business traffic switch to Concorde were over-optimistic, and there was disagreement over the predictions of Concorde operating costs. In the process of negotiating a sale of aircraft equipment, differences of this kind are not unusual, but on this occasion the gulf between the two sides was wide

enough to represent the difference between a profitable and a loss-making operation. And, despite a vigorous and highly professional marketing campaign, the gulf proved to be unbridgeable. On January 31 1973, the last day of the six months period, Pan American announced that it had decided to cancel its options. Within an hour, TWA announced a similar decision.

In its statement, Pan American said that its studies indicated that the "aeroplane will be capable of scheduled supersonic service," but that it would require substantially higher fares than today's and therefore did not satisfy the airlines' future requirements. TWA commended the technical achievements of the Concorde programme, but said that the first priority in the use of capital resources must be given to the improvement and expansion of its subsonic fleet.

Neither airline excluded the possibility that its interest in Concorde might be revived in the future. Pan American said that they would "maintain an open door to the manufacturers should they have any new proposals they wished to make." TWA said that they would maintain an interest in future developments of the programme and "would be available for discussions in the event of significant improvements in the viability of the airplane."

To Concorde supporters these pie-in-the-sky statements did little to soften their disappointment. Some people affected to see in the cancellations, coming so close together, a deep-laid plot to kill a European project that appeared to threaten American supremacy in the long-haul aircraft market. This supposition might have been a small sop to national pride but there was no evidence to support it. The decision to cancel had been taken on the airlines' assessment, however misguided it might be, of the economic viability of Concorde. It was no consolation to reflect how often airlines had been wrong in such assessments.

With his flair for the down-to-earth phrase, Sir George Edwards said: "This is a hell of a setback but it is not a mortal blow." It was a time for taking the long view, and neither the British nor the French government showed any sign of wavering in their support for the project. There would have to be some re-thinking on the manufacturing programme, but this would be directed towards a slow-down rather than a run-down. As expected, other operators, notably American Airlines and Eastern Airlines, followed Pan American and TWA in cancelling their options.

Although Concorde supporters made a speedy re-adjustment to the new situation, the psychological effects of the series of cancellations were depressing in the extreme. It could be argued that options were not orders and that it was wrong to regard a cancelled option in the same light as an order lost to a rival manufacturer. Yet whatever gloss was put upon the situation, the cold fact remained that Concorde had, for the time being, been rejected by a number of the world's most experienced operators

For critics of the project, the option setbacks provided excellent ammunition. They concentrated on the airline doubts about the economic viability of the aircraft, but here again Sir George Edwards gave a clear cut answer to the doubters. He pointed out that on British Airways' own estimates of Concorde operating costs and Concorde fare levels, the aircraft would break even

(including repayment of capital) at a load factor of 55.0 per cent. Since British Airways was thinking of a cabin layout with seating for around 100 passengers, that meant that Concorde would start to make a profit at an average load of about 55 passengers.

Even among the opposition - or, at least among those sections of the opposition with any knowledge of the aviation business - there was general agreement that Concorde would attract much more than a 55.0 per cent load factor. In the past even a modest increase in cruise speed had abstracted traffic from slower vehicles - and Concorde was going to half existing flight times.

American airlines' public criticisms of Concorde economics probably masked private fears about the revolutionary effect that the introduction of a supersonic airliner would have on the whole field of air transport. On its own account, Concorde could be operated at a profit; business travellers would be prepared, as one of them put it, "to pay real money for a real time saving." But what would be the effect on the economics of the subsonic fleet?

The makers' answer to this question was the mixed-fleet philosophy. But the validity of this new approach to airline marketing could not be demonstrated until Concorde had gone into service.

For the thousands of Frenchmen and Britons engaged on the Concorde project, the years 1973 and 1974 were a test of endurance, nerve, and teamwork. In the machine shops and on the assembly lines, in the laboratories and on the test rigs, in the computer centres and in the offices, the work went on. Sales teams toured the world, keeping airlines informed of progress.

The flight test programme also went ahead. The first significant event was the maiden flight from Toulouse on January 10 1973 of pre-production aircraft 02, the fourth Concorde to fly. It was significant because this was the first aircraft to be fitted with the new Mk 602-type Olympus 593 engines with the re-designed combustion chamber. As the aircraft took off, it could be seen that the smoke problem had indeed been cured. Instead of the twin black trails the prototypes had left behind them, there was only the faintest haze.

At about the same time, Concorde 002 began what was to prove to be a lengthy search for natural ice. Tests of the de-icing system had been made by flying Concorde behind a water tanker aircraft fitted with spraying equipment, but to meet the full requirements of the certification authorities it was necessary to demonstrate that the system could cope with a two-inch build-up of natural ice. 002 made a number of flights from Fairford in search of ice and later moved to Prestwick for further tests in more northerly latitudes, but without encountering severe enough conditions.

As if to underline the wide scope of the test programme, 002 was soon assigned to an entirely different task when it flew to South Africa for "hot and high" trials at Jan Smuts airport, Johannesburg. This airport is about 5,500ft. above sea level, and in January and February the temperature often exceeds 80°F. It is therefore a good location for establishing the effects of altitude and temperature on Concorde's airfield performance. Twenty-eight test flights were made, and the results obtained were within one per cent of prediction.

Because of its capacity for sustained supersonic flight, Concorde has been able to make important contributions to scientific knowledge. On June 30, 1973, for example, Concorde 001 provided scientists with the longest-ever sight of a total eclipse of the sun. Taking off from Las Palmas, it chased the moon's shadow at twice the speed of sound across Africa to the vicinity of Lake Placid. Seven scientists from French, British and American universities on board were able to take full advantage of 74 minutes of continuous observation of the eclipse. This record is likely to stand for 177 years as no eclipse of similar duration will occur until the year 2150.

For the Paris Air Show of 1973, marred by the crash of the Soviet TU 144 on the final day, pre-production aircraft 02 had the rear section of its cabin specially fitted out for VIP passenger travel. Typical French design flair was shown in the luxurious leather seating and the decor, and the final touch was provided by a wall-mounted Machmeter enabling passengers to check on the aircraft's speed. After the somewhat spartan interiors of the prototypes, 02 was a revelation and it gave many influential visitors to the Show a foretaste of what supersonic travel will really be like.

The year 1973 saw the effective completion of the two prototypes' contribution to the flight development programme. They had successfully fulfilled their purpose in establishing the basic design characteristics of Concorde and making the first exploration of the flight envelope. One of 002's last programmed operations was a further series of hot airfield trials at the Spanish airbase of Torreion, near Madrid. Concorde 001 was honourably retired to a French aviation museum at Le Bourget, but at the time of writing the final disposition of 002, which remains in an airworthy condition, has not been decided.

In September, 1973 Concorde made its first visit to the USA in response to an invitation to attend the inauguration of the new Dallas-Fort Worth airport. The first leg of the route took 02 from Paris to Caracas, a distance of nearly 5,200 miles. This was flown, including a refuelling stop at Las Palmas, in 6hr. 25min., thus cutting some five hours off the best subsonic scheduled time. During its four-day stay in Texas, Concorde 02 made supersonic demonstration flights over the Gulf of Mexico and proved to be the outstanding attraction in the flying displays, which formed part of the airport dedication ceremonies.

On Sunday, September 23, 02 flew to Dulles airport, Washington, D.C., and because of its ability to cruise at a higher subsonic speed than the conventional jets, staked a claim to be the world's fastest subsonic airliner by cutting 20 minutes off the Dallas-Dulles normal flight time.

In December, 1973 the first production standard Concorde took to the air. On its maiden flight from Toulouse it was airborne for three hours and flew supersonically for the better part of an hour. Although it was built essentially to the same standard as aircraft destined for airline service, this Concorde still carried a substantial quantity of special test equipment and was scheduled to continue flight development work for some years to come.

At the invitation of the Massachusetts Port Authority. 02 flew to Boston on June 13 to take part in the dedication of the new John Volpe international terminal. The Paris-Boston crossing set a new record at 3hr. 9min., and this was followed the next day by a rapid return flight to Miami.

On June 17, 02 showed its paces to spectacular effect. It took off from Boston at S.22a.m. and, at almost the same time, an Air France Boeing 747 left Paris en route for Boston. The two aircraft crossed when the 747 was 620 miles out of Paris and 02 was nearly 2,400 miles out of Boston. Despite the Concorde turn-round time at Paris being extended to 68 minutes because one passenger could not be found, at the end of its return flight it landed at Boston 11 minutes ahead of the 747. Five hundred businessmen from Brazil, the USA, West Germany, France, and Britain sampled and approved of supersonic travel on these two series of flights, and an estimated crowd of 100,000 people came to see the aircraft while it was on view at Boston, causing the biggest traffic jams ever known there.

In August came the counterpart of the Fairbanks trials when the second production aircraft set off for engineering systems tests in the tropical conditions of the Gulf It flew from Heathrow to Tehran and thence to Bahrain, where it was fitted out with 100 passenger seats, many of which had special seat-back probes to check on temperature distribution.

In the technical trials that followed Concorde's air conditioning system was thoroughly tested and its efficiency proven. Periods of hot soak on the ground were followed by flights with increasing numbers of passengers, culminating in a full 100 passenger load. During the flights, there were simulated failures of one or more elements of the air conditioning system. Even with only two of the four elements functioning, it was possible to maintain cabin temperature at a comfortable level.

In a nine-day demonstration tour in October, Concorde 02 once more underlined the point that it and the other Concordes had already made: that the age of supersonic travel is about to begin. The tour took 02 from Heathrow to Mexico City, via Gander (the first landing by Concorde on Canadian soil), and then on to San Francisco, Anchorage, Los Angeles, Lima, Bogota, Caracas and Las Palmas to Paris. As well as being a convincing marketing demonstration, the tour added to the build up of practical experience, as it included operations into seven unfamiliar airports, among them the high-altitude fields at Mexico City and Bogota, and two of the major gateways into the United States, San Francisco and Los Angeles.

Naturally, it was the show-piece tours such as this that made the headlines, but it is fitting to wind up this 1973-74 progress report with a brief mention of some less spectacular test operations which nevertheless made essential contributions to the main objective: qualifying the aircraft for the grant of a certificate of airworthiness.

In November and December, the first two production Concordes were engaged on certification trials at Casablanca, an airfield with important advantages for this kind of flight development programme. Part of the trials were concerned with engine intake functioning and Casablanca provides easy access to the cold high altitude regions in which the intake system is most severely tested. Another aspect of the trials was airfield noise measurement, and the unobstructed terrain around the Casablanca airfield is ideal for this.

And the search for that elusive natural ice was finally crowned with success. Concorde 01, operating in December from the Moses Lake airfield in the American northwest State of Washington, was at last able to achieve the required two-inch accretion of ice on the wing leading edge - and to demonstrate the de-icing system's efficiency.

These two years of intensive flight testing carried the certification programme well along the way towards completion, leaving the route-proving and endurance flying in the summer of 1975 as the final phase. When the great mass of test data acquired in the flight development programme had been analysed, every aspect of the aircraft's performance could be defined in specific detail. Now marketing discussion with airlines could be conducted on the basis of established fact rather than on prediction, however reasonable. How good, then, is the EIS (entry-into-service) aircraft? What kind of job will it do for the operators? With the support of the test results, the Concorde builders were able to give firm and positive answers to those questions. They felt able to say, without any qualification, that the EIS aircraft would exceed the contractual performance guarantees to Air France and British Airways by a substantial margin, and would be capable of carrying a full payload over more than 80 per cent of the world's supersonic route sectors.

Safety has, of course, been a vital consideration throughout the designing and testing of Concorde. It is appropriate to start with the human element, the flight crew. Nowhere has the collaboration of the airlines been more valuable than in the design and layout of the flight deck, which embodies the practical experience and advice of airline operators and pilots.

It is designed for operation by a crew of three: pilot, co-pilot, and a third crew member who is responsible for management of the aircraft systems. Throughout, the design aim has been to avoid any unnecessary departure from standard practice. The result is that flight crews feel immediately at home in the Concorde flight deck. Pilots' control columns are conventional in type and the general arrangement of the pilots' instruments and controls is similar to that in modern subsonic transports. Most of the instruments are familiar in their presentation, and the comparatively few new instruments are clear and easy to interpret.

To ease the workload of the flight crew, a full range of automatic flight systems is installed. The aircraft has two integrated autopilot-flight director systems, auto stabilisation, two auto-throttle systems, two independent air data systems and automatic landing facilities. An autopilot is, of course, a familiar feature but the flight director is new equipment which computes, and directs the aircraft to follow, the ideal flight path for take-off and ascent, taking into account all the relevant factors.

Auto-stabilisation enhances the natural stability of the aircraft, and so improves pilot control and passenger comfort. It smooths out the effects of air turbulence and should there be an engine failure, the system counters any tendency by the aircraft to yaw. However, even with the auto stabilisation system put out of action, the aircraft can be flown and controlled with ease. In flight testing, it will be recalled, Concorde has many times simulated the failure of two engines on the same side of the aircraft up to speeds of Mach 2, showing that the yaw effect can be readily controlled, with and without auto-stabilisation.

Concorde's navigation and communications system makes use of the most modern, and yet well-proven, equipment. A design requirement was that the aircraft must be capable of operation by two pilots without a navigator, and that the navigation system should enable the aircraft to fly anywhere in the world, with or without external aid.

By the spring of 1975, the first stage of the fatigue test programme on the full-size Concorde airframe specimen in the Royal Aircraft Establishment structures laboratory at Farnborough had been completed. A total of well over 8,000 flight cycles, equivalent to more than 18,000 flying hours, had been recorded and the subsequent inspection revealed no defects of any significance. Testing has been resumed and it is planned to continue up to a total of at least 48,000 flight cycles at a rate that will mean that the "life" achieved by the specimen is always three times as great as that of the first aircraft to go into passenger service.

Accident statistics show that take-off and the approach to land and touchdown are the most critical phases of the flight cycle, and Concorde has several built-in advantages at these times. Its power-to-weight ratio is higher than that of subsonic aircraft and this additional reserve of power is an important safety factor at take-off. The extra lift provided naturally by the air vortex formations over the wing at landing and take-off has already been mentioned and the fact that all mechanical high-lift devices (with their inherent liability to mechanical failure) can be dispensed with is another major "plus point." In the final phase of landing, the triangular wing compresses the air beneath, producing what is called the "ground cushion effect," another helpful feature.

In the course of years of ground testing and in thousands of hours of flight testing, the structural integrity of the Concorde airframe has been thoroughly proven. In many of the ground and flight tests, the structure has been deliberately subjected to loads far exceeding anything that would be encountered in actual operations.

Hydraulic power is used in Concorde for all the aircraft services in which a rapid and certain response to control movements is essential. These services include: flying control surfaces, landing gear, wheel brakes, nose wheel steering, visor, droop nose, the moving surfaces in the engine air intakes and the transfer pumps in the fuel system. There are three completely independent hydraulic power supply systems, with the Blue and the Green systems as the normal sources of supply and the Yellow system as the standby.

Particular attention has been paid in the system design to the maintenance of essential services in emergency. The failure of any two engines would still allow two of the three systems to be operated, and even the extremely unlikely event of a failure of all four engines has been provided for. Windmilling of the engines in glide descent from high altitude will provide sufficient hydraulic power for control of the aircraft to be maintained. If engine relight has not been obtained by the time the aircraft reaches a lower altitude, the emergency power unit will provide essential hydraulic power for aircraft control.

There is not space to deal with all the safety devices built into Concorde. It is however, worth mentioning two high-altitude environmental factors, cosmic radiation and ozone, which have sometimes been thought to present a potential health hazard. There are two types of cosmic radiation, galactic and solar. The infinitesimal amount of galactic radiation absorbed by supersonic passengers flying at higher altitudes is, because of the faster flight, actually less than that absorbed by subsonic passengers flying the same route.

Solar radiation is associated with solar flare, which occurs over a well-established cycle. Nevertheless, a radiation warning meter is installed on the flight deck, and, when this gives warning of a sudden increase in radiation intensity, the aircraft will descend to a lower altitude and continue its journey subsonically. Records show that this would have been necessary only five times in the last 39 years.

Ozone is a toxic gas, and it is present in measurable quantities in the atmosphere at the Concorde cruise altitude. There were fears that the cabin air supplied to the passengers would be contaminated by ozone since it is tapped from the engines which draw their air from the ambient atmosphere. However, any ozone present in the intake air is destroyed by the high temperature at which the engines operate, and in many tests simulating high-altitude operating conditions it has proved impossible to introduce any trace of ozone into the cabin. But again, to provide a safeguard, an ozone filter is fitted in the cabin air supply system.

The years Concorde has been under development have seen a world-wide growth in concern about the environment. Supersonic flight has inevitably been one of the targets. It has been possible to dismiss some of the scare stories - that passengers would have to remain seated, and that, because of cosmic radiation, we should be served only by stewardesses over child-bearing age - as the fantasies they were.

Sonic boom is a phenomenon inseparable from supersonic flight. Once an aircraft begins to exceed a speed of about Mach 1.15 (about 850mph), its shock waves start to reach the ground and a sonic boom is created. The sound can be heard across a corridor of up to 50 miles wide, the intensity being highest directly under the flight path of the aircraft but dying away to a faint rumble towards the edges of the corridor.

Because of its suddenness, sonic boom has a startling effect, especially when it is first experienced. Concorde's sonic boom will not cause physical damage to human beings or animals and the average "overpressure" (the sudden rise and fall in temperature at ground level) of about 161b. per square foot will not cause material damage to any structure in a reasonable state of repair. (To relate that overpressure to something in normal everyday experience, one can say that it is equivalent to the pressure one would feel when putting a hand out of the window of a car travelling at 30mph.)

It will be for individual governments to decide whether supersonic airliner operations can be permitted along carefully defined corridors through their national airspace. In some areas of the world, notably the Middle East, South America and Australia, supersonic corridors have been temporarily created in order that governments could assess the boom and test public reaction to it. Over oceans, sonic boom presents no problem. It has no effect on marine life, and in the course of Concorde's tours, many thousands of vessels of all sizes and types have been over flown without any adverse reports ever having been received.

Contrary to one popular misconception, there will also be no sonic boom problem in the locality of airports served by Concorde; in these localities, Concorde is a subsonic aircraft. After taking off, it will fly for about 100 miles before it reaches a speed at which it would start to create a boom, and at the other end of the journey it will be decelerating to a "non-boom" speed when it is still about 100 miles from its destination airport. Flight planning will also be so arranged as to place the acceleration boom over the sea or over a sparsely populated area.

Airfield noise is admittedly a more difficult problem. It is not possible to use a high bypass-ratio engine (a turbofan) in a supersonic airliner because the large frontal area of such engines would create unacceptable drag at supersonic speed. In the present state of the art, therefore, there is little prospect of making the Concorde engines as quiet as those of the second generation subsonic jets. This is not to say, however, that Concorde's airfield noise levels will be obtrusive

When at the time of the 1972 world tour, the early-development Olympus 593 engines in the prototype Concorde 002 were criticised as noisy, the airframe and aeroengine manufacturers stated that at entry into service the airfield noise levels of Concorde would be comparable with those of such well-known subsonic jets as the 707, the DC 8 and the VC 10. It was pointed out that many hundreds of these aircraft will continue in front-line service for many years after Concorde has started operation.

This forecast on noise levels has been made good. Measurements of engine noise in the approach, in fly-over and to the side of the runway are made at internationally agreed recording points, and independent measurements have confirmed the manufacturers' predictions. Concorde's overall airfield noise levels ire in the same "ballpark" as those of the first-generation subsonic jets, marginally worse in some respects and marginally better in others. In a series of test flights at Casablanca airport, Concorde demonstrated its ability to meet the stringent noise restrictions in force at J.F. Kennedy airport, New York.

The statement that Concorde's noise will not stand out from the general pattern of airport operations is borne out by experience on its overseas tours, during which it has visited some seventy airports in forty different countries. Concorde has flown into and out of these airports without arousing any special concern, despite the attempts of many local environmental groups to organise opposition to it.

Another charge laid against Concorde is that it will seriously increase ground level pollution at airports. The basis of this charge seems to be that when the aircraft is taxying, the level of carbon monoxide emission from its engines is slightly higher than that from subsonic aircraft engines. But within the airport complex, by far the greater amount of carbon monoxide comes not from aircraft, but from the fleets of ground servicing vehicles.

The most emotional and, in some ways, most damaging accusations levelled at supersonic airliners by the environmentalists have been concerned with stratospheric effects of high-altitude flying. Much of the emotion whipped up against the American SST - which provided the popular political support for its cancellation - was based on "scientific" theories which have since been shown to have been wildly exaggerated.

Ozone depletion is now the fashionable charge, but in the earlier years, there were other stratospheric bogies. There were suggestions that water vapour in the engine exhausts would create a permanent cloud barrier at high altitude flying, but there was no general agreement on what the result would be; one school forecast that the cloud layer would cut off much of the sun's heat and so bring about a new ice age on earth, and the opposite view was that the layer would create a "greenhouse" effect and send ground temperatures soaring.

These theories have now been discredited, but at the time they were first put forward they attracted worldwide attention. They were based on inadequate knowledge of the atmospheric circulation system in the stratosphere and they overlooked, or deliberately ignored, the fact that vast amounts of water vapour, far exceeding anything that could be produced by hundreds of aircraft, are daily injected into the stratosphere by tropical thunderstorms and other natural phenomena.

The main point of attack has now shifted to the alleged threat posed by Concorde to the ozone layer in the stratosphere. Opponents of SSTs allege that the nitrous oxides in the engine exhausts will partially erode the ozone layer allowing a higher intensity of ultra-violet radiation to penetrate to the earth's surface and so cause an increased incidence of skin cancer.

The most comprehensive programme of research into the possible effects of stratospheric pollution by aircraft is the Climatic Impact Assessment Programme (CIAP) mounted by the US Department of Transportation. This involved a number of other government departments and agencies in the USA and other countries and drew on the talents of 1,000 investigators in many American and foreign universities.

In the report of the CIAP findings, one of the principal conclusions was that operations of present-day supersonic airliners and those currently scheduled to enter service would cause climatic effects, which are much smaller than those minimally detectable. This minimum detectable change in global mean ozone was estimated by the Department of Transportation to be 0.5 per cent, and 100 Concordes each operating in the stratosphere for up to four and a half hours every day would have less than this effect. To set this minimum detectable change in perspective, the report pointed out that the natural fluctuation over Washington, DC, is 25 per cent and that there is a natural variation of as much as 30 per cent between Texas and Minnesota.

At a press conference to introduce the report, the director of the CIAP study project, Dr Alan Grobecker, described the SST as "merely a pimple" on the overall environmental problem compared with other sources of pollution. When asked to relate the 0.5 per cent reduction in ozone to skin cancer, Dr Grobecker said that this was the equivalent of 45 minutes on the beach.

One last accusation against Concorde remains to be answered. It is claimed that it will greatly hasten the rate at which the world's oil fuel resources are used up, and the rider is always added that this is happening merely to save businessmen a few hours' flying time. This criticism will not stand up to examination.

Admittedly, Concorde's fuel consumption is higher than that of current subsonic jets but the effect of this, against the world background, is negligible. The total consumption of oil fuel by civil aviation amounts to not more than six per cent of world consumption and on the most optimistic market estimates Concorde cannot be expected to take more than eight per cent of the total world air passenger market.

This would mean that Concorde would add rather less than 0.5 per cent to total world oil consumption. A small enough figure, but how does one make it comprehensible to the ordinary motorist? One way would be to say that if there are 30 years reserves of fuel left on earth, 100 Concordes operating daily throughout that period would shorten the 30 years by 20 days. So we need to look elsewhere for major savings in oil fuel, and ultimately, of course, we need to look to much-maligned technology to develop alternative sources of energy well before we run out of oil.

And what has it all cost? In 1962 the total bill was expected to be between £150 million and £170 million. In December, 1974, a written Parliamentary answer gave the information that the cost to Britain and France of developing Concorde up to the point at which it will enter airline service was then estimated to be £974 million. The three main factors responsible for this sixfold increase are inflation, currency devaluation and design changes. Inflation and devaluation have, in fact, been responsible for about 45 per cent of the increase. But why did the people who launched the project get the other costs so mistaken? The straight answer must be: "They would have needed to be superhuman to get them right." These men were trying to do something that had never been done before - build an aeroplane that would carry 100 passengers at twice the speed of sound - and they had no precedents for designing and marketing a supersonic airliner. The men in charge did not and could not, know what a jungle of problems they would have to hack their way through.

To look at it another way, Britain has invested, over 12 years, £40 million a year in Concorde. This is not a large sum when you compare it with the money paid by the British government to bail out collapsing industrial firms.

In straight accountancy terms, there will probably be no direct recovery of any part of the Concorde research and development costs. They must be regarded as part of our national investment in the future, part of the price we need to pay to retain our competitive position in a world where every nation is striving to achieve industrial self-sufficiency.

The demands of the Concorde programme have pushed forward the frontiers of knowledge, not only in the aerospace industry, but also in a number of other advanced technology industries, which have been called upon to provide supplies or services for the project. New managerial skills have been acquired, the use of computers in design and production applications have been greatly extended, new types of machine tools and new manufacturing techniques have been developed, and advances have been made in the technology of paints, glass, plastics, and non-ferrous metals - all because of Concorde. As a result of the spur to product improvement provided by Concorde, millions of pounds' worth of export business has been gained by British firms.

Until now, the Concorde story has been one of heavy financial outgoings, the only offset being in the somewhat indefinite area of spin-off. The extent to which Concorde will in the future make a measurable financial return to Britain depends on the level of overseas sales it achieves.

British Airways will soon start to earn useful sums of foreign currency from the sale of Concorde seats, but the real benefit to Britain's balance of payments will begin to accrue only after Concorde enters service with foreign operators. Every sale to an overseas airline would mean a substantial boost to this country's export earnings, not merely from the initial sale but from the continuing revenue derived throughout the aircraft's operating life, from overhauls, spares, and other product support activities. A relatively modest total sale of 50 aircraft overseas would bring in hundreds of millions of pounds over the next two decades.

But in reality it is far too early to strike any true balance. We have, in the development of air transport, almost certainly reached a "speed plateau" with Concorde.